Presynaptic facilitation: Quantal analysis and simulations

The time-course of quantal neurosecretion indicated asynchrony in releases of presynaptic vesicles (quanta) in response to a stimulus. This was interp reted as reflecting the sequential release of vesicles from a single releas e site. We performed Monte-Carlo simulation of facilitated neurosecretion b ased upon the hypothesis that release sites do not limit transmitter releas e. The output of this simulation succeeded in reproducing the experimentall y obtained distribution of quantal releases. These results support a. model for neurosecretion in which each action potential evokes mobilization of s ynaptic vesicles to a single presynaptic release site followed by probabili stic secretion of releasable vesicles one after another. (C) 1999 Elsevier Science B.V. All rights reserved.